JPH0125765B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing polyolefins. More specifically, the present invention relates to a method for producing a polyolefin with high polymerization activity and an extremely narrow molecular weight distribution using a novel catalyst containing a magnesium compound and a titanium compound. It is known that catalyst systems containing magnesium compounds and titanium compounds can be used for the polymerization of olefins. For example, JP-A-51-54889 discloses a catalyst system in which magnesium diethylate, titanium tetrabutyrate, and ethylaluminum dichloride are reacted, and JP-A-54-82395 discloses a catalyst system in which magnesium diethylate and halogen-containing titanium are reacted. Catalyst systems have been proposed in which a hydrocarbon-insoluble solid obtained from reaction with a compound is treated with an acid halide. When olefins were polymerized using these catalyst systems, the molecular weight distribution of the resulting polyolefins was somewhat narrow. In view of the fact that the mechanical properties and dimensional stability of polyolefins generally improve as the molecular weight distribution becomes narrower, the inventors of the present invention aimed to provide a polyolefin with an extremely narrow molecular weight distribution and an olefin with high polymerization activity. We have been studying polymerization catalysts. As a result, in a system that combines a magnesium compound and a titanium compound, a specific compound is used as the titanium compound, and a homogeneous hydrocarbon solution containing the magnesium compound, titanium compound, and in some cases a hydroxy compound is prepared, and this is The inventors have discovered that by treating with a halogenated silicon compound under specific conditions, a catalyst system that provides a polyolefin with an extremely narrow molecular weight distribution and high polymerization activity can be obtained, and the present invention has been achieved. That is, the gist of the present invention is that the general formula Mg(OR ² ) _n
X ² _2-n (wherein R ² represents an alkyl, aryl or cycloalkyl group, X ² represents a halogen atom,
m is 1 or 2) and the general formula Ti(OR ³ ) _o X ³ _4-o (wherein R ³ represents an alkyl, aryl or cycloalkyl group,
X ³ represents a halogen atom, n is 1, 2 or 3) and optionally a titanium compound of the general formula R ⁴ OH (wherein R ⁴ represents an alkyl, aryl or cycloalkyl group). ) A homogeneous hydrocarbon solution containing a hydroxy compound represented by the general formula R ¹ _l SiX ¹ _4-l (wherein R ¹ represents an alkyl, aryl or cycloalkyl group, X ¹ represents a halogen atom, and l represents a number of 0≦l≦2), the quantitative ratio of each compound, the number of moles of the magnesium compound, titanium compound, hydroxy compound, and halogenated silicon compound, respectively, When b, c, d, and a, between m, n, and l in the general formula, 1≦
(4-l)×a+(2-m)×b+(4-n)×c/m
Polymerizing ethylene or a mixture of ethylene and other α-olefins using a catalyst system consisting of a combination of a hydrocarbon-insoluble solid and an organoaluminum compound obtained in a ratio such that ×b+n×c+d<100. A method for producing a polyolefin is provided. To further explain the present invention in detail, the magnesium compound has the general formula Mg(OR ² ) _n X ² _2-n (wherein R ²
represents an alkyl, aryl or cycloalkyl group, X ² represents a halogen atom, and m is 1 or 2). Specifically, R ² is methyl, ethyl, propyl, butyl,
Alkyl, aryl, and cycloalkyl groups having up to about 15 carbon atoms, such as pentyl, hexyl, octyl, phenyl, tolyl, xylyl, and cyclohexyl, and compounds in which X ² is chlorine, bromine, or iodine, such as dimethoxymagnesium, dimethoxymagnesium, Examples include ethoxymagnesium, ethoxymagnesium chloride, diphenoxymagnesium, and the like. Among these, compounds in which m in the general formula is 2 are preferred. Among them, diethoxymagnesium is most suitable. On the other hand, titanium compounds have the general formula Ti(OR ³ ) _o
X ³ _4-o (wherein R ³ represents an alkyl, aryl or cycloalkyl group, X ³ represents a halogen atom,
n is 1, 2 or 3). Examples of R ³ and X ³ include those exemplified above ^for R ² and
- Propoxydichlorotitanium, di-n-butoxydichlorotitanium, etc.; Examples of compounds where n is 3 include triethoxymonochlortitanium, tri-n-propoxymonochlortitanium, tri-n-butoxymonochlortitanium; n is 1; Such compounds include ethoxytrichlortitanium, n-propoxytrichlortitanium, and n-butoxytrichlortitanium. Among these, those where n is 3 or 2, particularly those where n is 3 are preferred. Among them, tri-n-butoxymonochlorotitanium is most suitable. As the hydroxy compound, a compound represented by the general formula R ⁴ OH (wherein R ⁴ represents an alkyl group, an aryl group, or a cycloalkyl group) is used. Examples of the above R ⁴ include those exemplified above for R ² . Specific examples include ethyl alcohol, n-propyl alcohol, n-butyl alcohol, n-pentyl alcohol, and n-octyl alcohol. In the method of the present invention, a homogeneous hydrocarbon solution containing a magnesium compound, a titanium compound, and optionally a hydroxy compound as described above is first prepared. Examples of the hydrocarbon used as a solvent include aliphatic hydrocarbons such as hexane and heptane, alicyclic hydrocarbons such as cyclohexane, and aromatic hydrocarbons such as benzene, toluene, and xylene. In order to prepare a hydrocarbon solution, it is preferable to mix a magnesium compound, a titanium compound, and optionally a hydroxy compound in advance to prepare a homogeneous liquid. The order of mixing the three components is not particularly limited and may be arbitrary. After mixing, if the mixture is preferably heated to 100°C to 170°C, a uniform liquid or a uniform solution of the hydroxy compound can be obtained. Next, a hydrocarbon solvent is added to obtain a hydrocarbon solution, and the resulting hydrocarbon solution may be used to remove a hydroxy compound if a hydroxy compound is added thereto, but usually without substantially removing the hydroxy compound. Treatment with a halogenated silicon compound yields a hydrocarbon-insoluble solid. As a silicon halide compound, the general formula R ¹ _l
A compound represented by SiX ¹ _4-l (wherein R ¹ represents an alkyl, aryl or cycloalkyl group, and 1 represents a number of 0≦l≦2) is used. Examples of R ¹ and X ¹ in the general formula include those exemplified above for R ² and X ² . Among these, compounds in which X ¹ is chlorine are preferred. Specific examples include silicon tetrachloride, methyltrichlorosilane, ethyltrichlorosilane, propyltrichlorosilane, butyltrichlorosilane, phenyltrichlorosilane, diethyldichlorosilane, and the like. Among them, l=
The use of 0,1 chlorinated silicon compounds, especially silicon tetrachloride, gives favorable results. The halogenated silicon compound treatment can be carried out by adding the halogenated silicon compound to a homogeneous hydrocarbon solution and allowing the reaction to occur preferably at a temperature of 20 to 200°C. Since a hydrocarbon-insoluble solid is obtained, the solid is separated.
It may be washed with a hydrocarbon solvent. Therefore, the amount of each component is b, c,
When d and a are m, n, l in the general formula
Between 1≦
(4-l)×a+(2-m)×b+(4-n)×c/m
The ratio is selected such that ×b+n×c+d<100. Within this range, a catalyst can be obtained that provides a polyolefin with high polymerization activity and an extremely narrow molecular weight distribution. That is, if this value is less than 1.0, the polymerization activity will be significantly reduced. Moreover, if this value is 100 or more, it is not preferable from a practical point of view, such as the amount of the silicon halide compound used becomes very large, and the molecular weight distribution becomes somewhat wide. Further, in the above range, if 0.05≦b/c≦4, a catalyst with particularly high polymerization activity can be obtained. Next, as an organoaluminum compound used as a cocatalyst, for example, the general formula AlR ⁵ _p X ⁵ _3-p (in the formula,
R ⁵ represents an alkyl, aryl or cycloalkyl group, X ⁵ represents a halogen atom, and p is 1 to 3
(indicating the number of ).
Examples of R ⁵ and X ⁵ include those exemplified as R ² and X ² . Specifically, trialkylaluminum such as triethylaluminum, tri-n-propylaluminum, and triisobutylaluminum is preferred. The proportion of the hydrocarbon-insoluble solid and the organoaluminum compound used is usually within the range of 0.1 to 100, preferably 1 to 20, in terms of Al/Ti atomic ratio. The catalyst system thus prepared is used to carry out the polymerization of ethylene or mixtures of ethylene and other α-olefins. Other α-olefins include propylene, butene-1, pentene-1, octene-1, and the like. The polymerization reaction can be carried out by solution polymerization or slurry polymerization carried out in an inert solvent, or by gas phase polymerization carried out in the absence of a solvent. This is usually carried out by supplying the olefin or olefin mixture and maintaining it at a predetermined temperature and pressure in the presence of an inert solvent.
As the inert solvent, aliphatic hydrocarbons such as pentane, hexane, heptane, octane, and isooctane, and aromatic hydrocarbons such as benzene and toluene are used. The polymerization reaction is usually carried out at a temperature of from room temperature to 200°C and a pressure of from normal pressure to 100 atmospheres. Further, in the method of the present invention, when hydrogen is present in the polymerization reaction zone, the effect of controlling the molecular weight by hydrogen is large, and a polymer having a desired molecular weight can be easily obtained. The amount of hydrogen to be present varies depending on the polymerization conditions, the desired molecular weight of the olefin polymer, etc., and therefore it is necessary to adjust the amount of hydrogen introduced accordingly. The polyolefin produced by using the catalyst system obtained by the method of the present invention as described above has an extremely narrow molecular weight distribution. In other words, the following
Polyolefins with an FR value of 20 or less can be easily obtained. Therefore, this polyolefin not only has excellent mechanical properties and dimensional stability, but also has a low amount of grease wax by-product during the production of polyolefin, and contains less hydrocarbons among the reaction products of magnesium compounds and titanium compounds. Since it is obtained using only soluble components, the polymer produced by the method of the present invention has the characteristic that it is extremely difficult to form fish eyes. Next, the present invention will be explained in more detail with reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist thereof. In the examples, the polymerization activity K of the catalyst was expressed as K=(g polymer)/(g·catalyst) (hr) (Kg/cm ² olefin pressure). Also, the melt index is
2.16Kg at 190℃ based on ASTM・D・1238・57T
It was measured by load and expressed in MI. Furthermore, the flow rate ratio (hereinafter abbreviated as FR), which is a measure of molecular weight distribution, is a value that indicates the dependence of melt viscosity on shear stress, and is a value specified by ASTM.
According to D・1238・57T, it is expressed as the ratio of melt index measured at shear stress of 10 ⁶ dyne/cm ² and 10 ⁵ dyne/cm ² , and the larger the FR, the broader the molecular weight distribution, and the smaller the molecular weight distribution. If so, it is considered narrow.
Further, FIG. 1 is a flowchart diagram to help understand the technical content included in the present invention, and the present invention is not limited in any way by the flowchart diagram as long as it does not deviate from the gist thereof. Examples 1 to 3 26 mmol of magnesium diethylate and a predetermined amount of tri-n-butoxymonochlorotitanium were mixed and stirred at 140°C for 4 hours to obtain a homogeneous liquid. After cooling to 80°C, a predetermined amount of benzene was added to form a homogeneous solution. A predetermined amount of silicon tetrachloride was added thereto at 40°C, and then stirred for 3 hours at the temperature listed in Table 1 to ripen. The generated precipitate was washed with n-hexane and subjected to polymerization in the form of n-hexane slurry. Next, put normal hexane in 1 autoclave.
500 c.c. was taken and charged with 10 mg of the above solid powder. 90
After raising the temperature to .degree. C., hydrogen was introduced to 2 Kg/ ^cm.sup.2 , and 0.16 mmol of triethylaluminum was introduced together with ethylene to bring the total pressure to 8 Kg/ ^cm.sup.2 (gauge pressure). Ethylene absorption is seen with the introduction of ethylene,
Ethylene was additionally introduced to maintain the total pressure at 8 Kg/cm ² , and 1 hour later, the polymerization was stopped by pressurizing ethanol. The results obtained are shown in Table 1. G in Table 1 is G=
(4-l)×a+(2-m)×b+(4-n)×c/m
It represents the value of xb+nxc+d. Example 4 3 g (26 mmol) of magnesium diethylate, 3.9 g (13 mmol) of tributoxymonochlorotitanium, and 0.96 g (13 mmol) of n-butanol were mixed and heated at 140°C.
The mixture was stirred for 4 hours to obtain a homogeneous liquid. Then 80℃
After allowing the mixture to cool, 60 ml of benzene was added to make a homogeneous solution. Here, 35g (206mmol) of silicon tetrachloride at 40℃
was added and stirred at 50°C for 3 hours. The generated precipitate was washed with n-hexane and subjected to polymerization in the form of n-hexane slurry. Polymerization was carried out in exactly the same manner as in Example 1 except that the above solid catalyst component was used, MI = 0.20, FR17
150g of polyethylene was obtained. K=2900. Example 5 A solid catalyst component was prepared in exactly the same manner as in Example 1 except that 728 mmol of phenyltrichlorosilane was used instead of silicon tetrachloride, and polymerization was carried out in the same manner as in Example 1 except for using this solid catalyst component. I did this. As a result, 138 g of polyethylene with MI=0.18 and FR16 was obtained. K=2650. Example 6 In the ethylene polymerization of Example 2, butene-1 was mixed when introducing and adding ethylene, and the molar ratio of butene-1/ethylene in the gas phase during the polymerization reaction was
Copolymerization of ethylene and butene-1 was carried out in exactly the same manner except that the copolymerization ratio was 0.05. As a result, 221 g of polymer with MI=0.25 and FR16 was obtained. The polymer was an ethylene-butene-1 copolymer containing 0.8 mole percent butene-1 units. Comparative Example 1 In Example 1, the amount of silicon tetrachloride was
A solid catalyst component was prepared in exactly the same manner except that the amount was 10 mmol. At this time, G=0.5. Polymerization was carried out in exactly the same manner as in Example 1 except that this solid catalyst component was used, and 9.5 g of polyethylene with MI=0.19 and FR16 was obtained. The polymerization activity K was 180. As described above, when G<1, the polymerization activity of the obtained catalyst is low. Comparative Example 2 3 g (26 mmol) of magnesium diethylate was suspended in 80 ml of benzene, and 5 g (26 mmol) of titanium tetrachloride was added thereto at room temperature. The system did not become a homogeneous solution, but instead became a grayish-white slurry. then 40
Add 13.3g (78.3mmol) of silicon tetrachloride at ℃,
Stirring was performed at 50°C for 3 hours. The generated precipitate was washed with n-hexane and subjected to polymerization in the form of n-hexane slurry. Polymerization was carried out in exactly the same manner as in Example 1, except that the above-mentioned solid catalyst component was used, and 18 g of polyethylene with MI=0.32 and FR24 was obtained. The polymerization activity K was 350. 【table】

[Brief explanation of drawings]

FIG. 1 is a flowchart showing one embodiment of the present invention.

Claims (1)

[Claims] 1 General formula Mg(OR ² ) _n X ² _2-n (wherein R ² represents an alkyl, aryl or cycloalkyl group, and X ²
represents a halogen atom, m is 1 or 2), a magnesium compound represented by the general formula Ti(OR ³ ) _o X ³ _4-o (wherein R ³ is alkyl,
aryl or cycloalkyl group, X ³ is a halogen atom, n is 1, 2 or 3) and optionally a titanium compound of the general formula R ⁴ OH (wherein R ⁴ is A homogeneous hydrocarbon solution containing a hydroxy compound of the general formula R ¹ _l SiX ¹ _4-l (wherein R ¹ represents an alkyl, aryl or cycloalkyl group) is added to , X ¹ represents a halogen atom, l represents a number of 0≦l≦2), the quantitative ratio of each compound is determined as follows: magnesium compound, titanium compound, hydroxy compound and When the number of moles of the silicon halide compound is b, c, d, and a, respectively, between m, n, and l in the general formula, 1≦
(4-l)×a+(2-m)×b+(4-n)×c/m
Polymerizing ethylene or a mixture of ethylene and other α-olefins using a catalyst system consisting of a combination of a hydrocarbon-insoluble solid and an organoaluminum compound obtained in a ratio such that ×b+n×c+d<100. A method for producing polyolefin characterized by: 2 As a magnesium compound, the general formula Mg(OR ² ) ₂
The method for producing a polyolefin according to claim 1, which uses a compound represented by the formula Ti(OR ³ ) ₃ X ³ as the titanium compound. 3. The method for producing a polyolefin according to claim 1 or 2, wherein magnesium diethylate is used as the magnesium compound and tri-n-butoxymonochlorotitanium is used as the titanium compound. 4. The method for producing a polyolefin according to any one of claims 1 to 3, using a compound in which X ¹ is chlorine and l = 0 or 1 as the halogenated silicon compound. 5. The method for producing a polyolefin according to any one of claims 1 to 4, in which silicon tetrachloride is used as the halogenated silicon compound. 6. The amount of the magnesium compound and the titanium compound satisfies 0.05≦b/c≦4, where b and c represent the number of moles, respectively, according to any one of claims 1 to 5. The method for producing the polyolefin described.